1. Field of the Invention
The present invention relates to a controller-assisted, manually shifted vehicular transmission system including a splitter-type compound transmission. The system will sense very low vehicle speed, master clutch disengagement, and a shift into main section neutral and will automatically shift the splitter section into neutral, allowing the main section to be engaged into a target start ratio without excess wear on, or the need for, a clutch brake. Upon sensing completion of the main section shift into a target start ratio, the splitter section will be caused to engage in an appropriate splitter ratio.
More particularly, in a preferred embodiment of the present invention, a splitter or combined splitter-and-range-type compound synchronized transmission for heavy-duty vehicles is provided with controls and actuators for manually performed main section start ratio engagement shifting without requiring excessive wear on or the use of a clutch brake.
2. Description of the Prior Art
Compound manually shifted mechanical transmissions of the range, splitter and/or combined range/splitter type are in wide use in heavy-duty vehicles and are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,754,665; 5,272,929; 5,370,013 and 5,390,561, 5,546,823; 5,609,062 and 5,642,643, the disclosures of which are incorporated herein by reference. Typically, such transmissions include a main section shifted directly or remotely by a manual shift lever and one or more auxiliary sections connected in series therewith. The auxiliary sections most often were shifted by a slave actuator, usually pneumatically, hydraulically, mechanically and/or electrically operated, in response to manual operation of one or more master switches. Shift controls for such systems by be seen by reference to U.S. Pat. Nos. 4,455,883; 4,550,627; 4,899,607; 4,920,815; 4,974,468; 5,000,060; 5,272,931; 5,281,902; 5,222,404; 5,350,561 and 5,737,696, the disclosures of which are incorporated herein by reference.
Three-position splitter actuators and transmission systems utilizing same are disclosed in U.S. Pat. Nos. 5,651,292 and 5,661,998, the disclosures of which are incorporated herein by reference.
Fully or partially automated transmission systems wherein a microprocessor-based electronic control unit (ECU) receives input signals indicative of various system operating conditions and processes same according to logic rules to issue command output signals to one or more system actuators are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,593,580; 4,595,986; 4,850,236; 5,435,212; 5,582,069; 5,582,558; 5,620,392; 5,651,292; 5,679,096; 5,682,790 and 5,735,771; the disclosures of which are incorporated herein by reference.
U.S. Pat. No. 4,527,446, the disclosure of which is incorporated herein by reference, discloses a fully automated, blocked-type transmission wherein the main section is automatically shifted to main section neutral during each shift.
Clutch brakes, also called start brakes, are known in the prior art, as may be seen by reference to U.S. Pat. No. 5,713,443, the disclosure of which is incorporated herein by reference. Clutch brakes are used to retard spinning of the transmission input shaft caused by inertia and/or random clutch engagement when the master clutch is fully disengaged to allow engaging of a start ratio in a stopped or substantially stopped vehicle. In manual systems, actuation of the clutch brake is often by overtravel of the clutch pedal.
The provision, installation, maintenance and/or adjustment of a clutch brake can involve considerable time and expense. The clutch brake can be misused as an upshift brake to allow for more rapid dynamic upshifts, which may result in excessive wear and/or damage to the clutch brake.
A preferred embodiment of the present invention involves a computer-assisted mechanical compound transmission system wherein the main section is provided with jaw clutches and is shifted by a manually controlled shift lever, and the engine is fueled and/or the auxiliary sections are shifted by actuators at least partially controlled by an ECU to enhance shifting. The ECU uses sensed and/or calculated inputs indicative of system operating parameters, such as vehicle speed, master clutch condition, position and/or rate of change of position of the shift lever, engaged gear ratio, engine speed, output shaft speed and/or throttle pedal position, to assist shifting by controlling the three-position splitter actuator shift actuator and, preferably, also engine fueling and/or operation of the range shift actuator.
In accordance with the present invention, the drawbacks of the prior art are minimized or overcome by the provision of a control method/system that includes logic rules or an algorithm using a number of inputs to determine when the vehicle is at rest, the master clutch is disengaged and the main transmission section is in neutral, and to automatically cause the splitter section to be shifted into splitter section neutral. This will minimize the wear on and/or the need for a clutch brake by reducing the inertia of the rotating elements being clutched by the main section jaw clutches, allowing the main section to be engaged in a start ratio considerably out of synchronous, while not causing an objectionable amount of wear or harshness to the vehicle operator.
By use of the control of the present invention, wear, misuse and damage to the clutch brake can be minimized or the need for a clutch brake eliminated. This will provide savings in initial costs and installation, maintenance and/or adjustment costs.
Accordingly, it is an object of the present invention to provide ECU assistance for enhanced shifting of a mechanical compound splitter-type transmission into a start ratio with minimal or no requirement for a clutch brake.
This and other objects and advantages of the present invention will become apparent from a reading of the following description of the preferred embodiment taken in connection with the attached drawings.